Personally speaking, yes it is worth it. Why do i say that? Because you get all templates including updates for a year. I have purchased the full package in September and If a new theme gets out, i get it for free.

I think you should ask yourself how serious you want to go into Mobirise. If you are just testing, no you do not need it.

Well, I bought the full package on Black Friday and now I see a new theme Strategy AMP and I cannot get it, only available to buy, despite the fact that Mobirise said I will get all new stuff free for a year.